1. Field of the Invention
The present invention relates to a printing apparatus and control method thereof and, more particularly, to control processing when successively printing a plurality of calendar sheets with images on roll paper.
2. Description of the Related Art
A dye sublimation printer using roll paper can print a plurality of images successively at a paper size equal to or larger than the ribbon set unit by changing the paper cutting position. In general, yellow (Y), magenta (M), and cyan (C) sublimation dye layers and an overcoat (OC) layer for protecting an image forming layer are repetitively arranged on a base frame-sequentially in the conveyance direction on an ink ribbon used in a thermal transfer color printer. To form one image, Y, M, C, and OC, which form one cycle, are thermally transferred onto paper sequentially. In this specification, a unit corresponding to the length of an ink ribbon used for printing of one cycle will be called a “ribbon set unit”.
In this printing method, the printer driver can rasterize data while automatically determining the data rotation angle in synchronization with functions such as banner printing, rotation, and mirror image. In some cases, the printing order can be reversed (see, for example, Japanese Patent Laid-Open No. 2006-163693).
A case where two monthly calendar sheets with images such as pictures are printed successively will be examined. FIGS. 2A and 2B exemplify printing results by a conventional method. FIG. 2A shows a printing result when a calendar sheet of the first month is printed with a 1.5-ribbon set unit of the ink ribbon and calendar sheets of two months are printed successively. More specifically, as shown in FIG. 2A, an image area such as a picture is printed in the area of a first ribbon set 201, and a date area is printed in a left half area 203 of a second ribbon set 202 beside the image area. When thus-obtained data of two months are printed successively, the picture becomes unnatural at a boundary 204 between the second and third ribbon sets. This problem is specific to dye sublimation printers and arises because the temperature of the thermal head has not risen satisfactorily at the beginning of printing and ink does not sublimate sufficiently.
To solve the above problem, printing as shown in FIG. 2B can prevent generation of the boundary 204 of the ribbon set in the image area in the conventional method. More specifically, an image area 211 of the first calendar sheet is printed in the area of the first ribbon set. Then, the date area is printed in a left half area 212 of the second ribbon set, and the right half is printed as an unprinted area 213. The second calendar sheet is printed using the third and subsequent ribbon sets, similar to the first calendar sheet. However, this method wastes the ink ribbon and paper by the unprinted areas 213.